Embedded flat film molding

ABSTRACT

A flat filter layer is received between upper and lower mold portions of a mold for packaging an integrated circuit sensor device, held by the mold over and in contact with the integrated circuit&#39;s sensing surface, in light compression between the sensing surface and a mold surface. The filter layer includes slots allowing passage of injected encapsulating material to cover the integrated circuit die, with overlap portions embedded in the encapsulating material, while preventing such encapsulating material from flowing onto the sensing surface. The filter layer may be, for example, a liquid and/or light filter, and may include a protective or supportive backing. The filter is thus affixed to the packaged integrated circuit sensor device, while mold residue is reduced and mold life extended.

TECHNICAL FIELD OF THE INVENTION

The present invention is directed, in general, to packaging integratedcircuits and, more specifically, to packaging integrated circuit sensorshaving an exposed sensing surface requiring protection by a filter.

BACKGROUND OF THE INVENTION

Certain types of integrated circuit sensors, such as capacitivefingerprint sensors and optical sensors for scanners, fax machines, andthe like, require that a portion of the packaged integrated circuitremain exposed. The sensing surface, below which an array of (forexample) capacitive electrodes or optoelectronic devices is located,generally cannot be encapsulated with the remainder of the integratedcircuit, but must remain exposed in order to perform the functionintended.

Sensing surfaces may, however, require protective filters. A fluid(liquid or air) filter may be required to exclude contaminants of atleast a certain particle or molecular size, or a light filter excludingor passing a particular wavelength/color of incident light may beneeded. Such filters should preferably be attached to the sensorintegrated circuit before use (i.e., before shipping from production).

There is, therefore, a need in the art for improved methods of affixingfilters to sensor integrated circuit devices.

SUMMARY OF THE INVENTION

To address the above-discussed deficiencies of the prior art, it is aprimary object of the present invention to provide, for use in packagingan integrated circuit sensor device having a sensing surface, a flatfilter layer received between upper and lower mold portions of a moldfor packaging an integrated circuit sensor device, held by the mold overand in contact with the integrated circuit's sensing surface, in lightcompression between the sensing surface and a mold surface. The filterlayer includes slots allowing passage of injected encapsulating materialto cover the integrated circuit die, with overlap portions embedded inthe encapsulating material, while preventing such encapsulating materialfrom flowing onto the sensing surface. The filter layer may be, forexample, a liquid and/or light filter, and may include a protective orsupportive backing. The filter is thus affixed to the packagedintegrated circuit sensor device, while mold residue is reduced and moldlife extended.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention so that those skilled in the art maybetter understand the detailed description of the invention thatfollows. Additional features and advantages of the invention will bedescribed hereinafter that form the subject of the claims of theinvention. Those skilled in the art will appreciate that they mayreadily use the conception and the specific embodiment disclosed as abasis for modifying or designing other structures for carrying out thesame purposes of the present invention. Those skilled in the art willalso realize that such equivalent constructions do not depart from thespirit and scope of the invention in its broadest form.

Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, itmay be advantageous to set forth definitions of certain words or phrasesused throughout this patent document: the terms “include” and“comprise,” as well as derivatives thereof, mean inclusion withoutlimitation; the term “or” is inclusive, meaning and/or; the phrases“associated with” and “associated therewith,” as well as derivativesthereof, may mean to include, be included within, interconnect with,contain, be contained within, connect to or with, couple to or with, becommunicable with, cooperate with, interleave, juxtapose, be proximateto, be bound to or with, have, have a property of, or the like; and theterm “controller” means any device, system or part thereof that controlsat least one operation, whether such a device is implemented inhardware, firmware, software or some combination of at least two of thesame. It should be noted that the functionality associated with anyparticular controller may be centralized or distributed, whether locallyor remotely. Definitions for certain words and phrases are providedthroughout this patent document, and those of ordinary skill in the artwill understand that such definitions apply in many, if not most,instances to prior as well as future uses of such defined words andphrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, wherein likenumbers designate like objects, and in which:

FIG. 1 depicts an exploded side cross-sectional view of a moldingmechanism for affixing filters to integrated circuit sensor devicesduring packaging according to one embodiment of the present invention;

FIG. 2 is a plan view of an integrated circuit sensing surface filterlayer for use in affixing filters to integrated circuit sensor devicesduring packaging according to one embodiment of the present invention;and

FIGS. 3A and 3B depict plan and side elevation views, respectively, of apackaged integrated circuit sensor device having a filter affixed duringpackaging according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 through 3B, discussed below, and the various embodiments used todescribe the principles of the present invention in this patent documentare by way of illustration only and should not be construed in any wayto limit the scope of the invention. Those skilled in the art willunderstand that the principles of the present invention may beimplemented in any suitably arranged device.

FIG. 1 depicts an exploded side cross-sectional view of a moldingmechanism for affixing filters to integrated circuit sensor devicesduring packaging according to one embodiment of the present invention.Molding mechanism 100 consists of a mold 101 (hatched regions), which inthe exemplary embodiment includes a bottom mold portion 101 a, a spacer101 b, and a top mold portion 101 c.

The bottom mold portion 101 a includes an inset 102 for receiving anintegrated circuit die 103 and the packaging substrate 104 on which theintegrated circuit die 103 is mounted. In the exemplary embodiment, themold 101 (particularly the bottom mold portion 101 a and the spacer 101b) is designed to encapsulate only the integrated circuit die 103 and atleast a portion of the upper surface of the packaging substrate 104,with the packaging substrate 104 serving as the bottom of the packagedintegrated circuit.

The upper mold portion 101 c includes inset(s) 105 for formingprojections on the packaged integrated circuit, and is sized to providea space around the integrated circuit die 103 (when the mold 101 andintegrated circuit die 103/packaging substrate 104 are assembled) intowhich encapsulating material is injected. Injection passages (notshown), typically opening into inset(s) 105 allow injection of theencapsulating material (e.g., thermo-setting plastic or epoxy resin)when the mold 101 and integrated circuit die 103/packaging substrate 104are assembled.

In the present invention, a flat filter layer 106 is positioned betweenthe spacer 101 b and the upper mold portion 101 c during assembly, atthe same height as and with a portion 106 a in contact with the (upper)sensing surface 103 a of the integrated circuit die 103 contained withinthe mold 101. After assembly, filter layer 106 overlies integratedcircuit die 103, including any passivation or protective layers (e.g.,silicon oxide, silicon carbide, silicon nitride, metal or organicmaterial layers, etc.) formed thereon during fabrication of theintegrated circuit.

The filter layer 106 is received between the spacer 101 b and the uppermold portion 101 c. The bottom mold portion 101 a, spacer 101 b, andlower mold portion 101 c are adapted to hold filter layer 106 at thesame height as the sensing surface of the integrated circuit die 103when assembled. The portion 106 a of filter layer 106 that contacts thesensing surface of integrated circuit die 103 also contacts a surface ofthe upper mold portion 101 c, and may be held in light compressiontherebetween when mold 101, integrated circuit die 103/packagingsubstrate 104, and filter layer 106 are assembled.

The filter layer 106 may be a fluid filter, a light filter, or anothertype of filter, depending upon the sensing nature of the integratedcircuit die 103 and the particular exclusion requirements (e.g.,contaminants and/or filtered light). Although illustrated as a singlelayer, filter 106 may comprise multiple layers. In addition, filterlayer 106 may include the filtering material mounted on a backing orprotective layer (e.g., paper) during manufacture which is removed aftercompletion of the molding process.

In other integrated circuit sensor device packaging schemes, a flexiblematerial is employed to protect the active sensing surface duringmolding, such as a flexible material formed in-situ (within the mold) byvacuum, a screen-on gasket material on the integrated circuit sensingsurface, or a cushion material attached onto the mold surface thatcontacts the sensing surface of the integrated circuit die. Thesetechniques require pre-forming of the protective layer, sacrifice ofintegrated circuit area, and/or regular mold cleaning (which may affectmold life). In the present invention, however, filter layer 106 requiresminimal pre-forming, does not require dedicated integrated circuitsurface area, and, particularly with a protective backing, or specialcoating (either formed discretely or by impregnating the film withchemicals or enzymes) on the film, does not leave a residue in the mold.

FIG. 2 is a plan view of an integrated circuit sensing surface filterlayer for use in affixing filters to integrated circuit sensor devicesduring packaging according to one embodiment of the present invention.FIG. 2 is intended to be read in conjunction with FIG. 1.

Filter layer 106 includes one or more slots 107 there-through, allowinginjected encapsulating material to pass through the filter layer 106 andcontact the integrated circuit die 103. Slots 107 are surrounded by abuffer region 108 overlapping the surface portions of the integratedcircuit die 103 beneath the cavities 105 within the upper mold portion101 c. After molding, the overlap areas 108 will be embedded in themolded encapsulating material, helping provide retention of the filterlayer 106 in place. The portion 106 a of filter layer 106 which contactsthe sensing surface 103 a of the integrated circuit die 103 (and asurface of upper mold portion 101 c after assembly) preventsencapsulating material from being injected onto the sensing surface 103a, leaving that surface exposed after molding. After molding, excessareas of the filter layer 106 (e.g., around the periphery of thepackaged integrated circuit) are removed by, for example, laser cutting.Any protective or supportive backing for the filter material withinfilter layer 106 may also be removed at that time.

FIGS. 3A and 3B depict plan and side elevation views, respectively, of apackaged integrated circuit sensor device having a filter affixed duringpackaging according to one embodiment of the present invention. As notedabove, the bottom of the packaged integrated circuit sensor device 300is formed by packaging substrate 301. Encapsulation material 302injected into the mold hardens over packaging substrate 301 and aroundthe integrated circuit die, forming projections 303 where the upper moldportion cavities are located and leaving sensing surface 304 of theintegrated circuit die exposed except for coverage by filter layer 305.Portions of filter layer 305 are embedded in encapsulating material 202,particularly in the area of projections 303.

Although the present invention has been described in detail, thoseskilled in the art will understand that various changes, substitutions,variations, enhancements, nuances, gradations, lesser forms,alterations, revisions, improvements and knock-offs of the inventiondisclosed herein may be made without departing from the spirit and scopeof the invention in its broadest form.

1. A mold assembly for packaging an integrated circuit sensor devicecomprising: a flat filter layer; and a mold adapted to receive thefilter layer and an integrated circuit die having a sensing surface, themold maintaining the filter layer in contact with the sensing surfacewhen assembled with the integrated circuit die and the filter layer, themold defining an enclosure into which material is selectively injectedto encapsulate the integrated circuit die while leaving the sensingsurface exposed except for coverage by the filter layer, wherein thefilter layer has openings positioned to permit passage of theencapsulating material therethrough during injection of theencapsulating material into the mold.
 2. The mold assembly according toclaim 1, wherein the mold further comprises: an upper portion and alower portion, wherein the filter layer is received between the upperand lower portions and held in compression between the sensing surfaceand a mold surface.
 3. The mold assembly according to claim 2, whereinthe mold assembly further comprises: a spacer between the upper andlower portions, the spacer restricting the encapsulating material to anupper surface of a packaging substrate on which the integrated circuitdie is mounted during injection of the encapsulating material into themold.
 4. The mold assembly according to claim 1, wherein the openingsthrough the filter layer are sized to create filter layer overlapregions with cavities within the mold, wherein the overlap regions areembedded within the encapsulating material after packaging.
 5. The moldassembly according to claim 4, wherein the cavities correspond toprotrusions on a packaged integrated circuit sensor device afterpackaging.
 6. The mold assembly according to claim 4, wherein theoverlap regions provide retention of the filter layer on the sensingsurface of the integrated circuit die after packaging.
 7. The moldassembly according to claim 1, wherein the filter layer comprises afluid filtration material or a light filtration material.
 8. A packagedintegrated circuit sensor device comprising: a flat filter layer havingopening therethrough; an integrated circuit die having a sensingsurface, the filter layer in contact with the sensing surface; andencapsulation material surrounding at least a portion of the integratedcircuit die while leaving the sensing surface exposed except forcoverage by the filter layer, wherein the encapsulation material extendsthrough the openings in the filter layer to contact the integratedcircuit die.
 9. The packaged integrated circuit sensor device accordingto claim 8, wherein the filter layer is held in contact with the sensingsurface by the encapsulation material.
 10. The packaged integratedcircuit sensor device according to claim 8, further comprising: apackaging substrate on which the integrated circuit die, theencapsulation material extending over only an upper surface of thepackaging substrate.
 11. The packaged integrated circuit sensor deviceaccording to claim 8, wherein the openings through the filter layer aresized to overlap portions of the integrated circuit die surface on whichthe encapsulation material is formed, wherein the overlap regions areembedded within the encapsulation material.
 12. The packaged integratedcircuit sensor device according to claim 11, wherein the overlapportions underlie protrusions of the encapsulation material.
 13. Thepackaged integrated circuit sensor device according to claim 11, whereinthe overlap portions provide retention of the filter layer on thesensing surface of the integrated circuit die.
 14. The packagedintegrated circuit sensor device according to claim 8, wherein thefilter layer comprises a fluid filtration material or a light filtrationmaterial.
 15. A packaged integrated circuit, comprising: a filtercomprising at least one opening; an integrated circuit die comprising asensing surface; and an encapsulation material operable to maintain thefilter in contact with the sensing surface, the encapsulation materialextending through the at least one opening of the filter and in contactwith the integrated circuit die.
 16. The packaged integrated circuit ofclaim 15, further comprising a packaging substrate, the integratedcircuit die disposed on the packaging substrate.
 17. The packagedintegrated circuit of claim 15, wherein the filter comprises at leastone buffer region, the at least one buffer region embedded within theencapsulation material so as to maintain the filter in contact with thesensing surface of the integrated circuit die.
 18. The packagedintegrated circuit of claim 17, wherein the encapsulation materialcomprises one or more projections, each of the projections formed overone or more of the buffer regions of the filter.
 19. The packagedintegrated circuit of claim 18, wherein the one or more projections areformed by one or more cavities in a mold into which the encapsulationmaterial was injected.
 20. The packaged integrated circuit of claim 15,wherein the filter comprises at least one of a fluid filtration materialand a light filtration material.